Math-genius mercenary Cas Russell has decided to Fight Crime(tm). After all, with her extraordinary mathematical ability, she can neuter bombs or out-shoot an army. And the recent outbreak of violence in the world's cities is Cas's fault-she's the one who crushed the organization of telepaths keeping the world's worst offenders under control. But Cas's own power also has a history, one she can't remember-or control. One that's creeping into her mind...